A refrigerant evaporator functions as a cooling heat exchanger that cools fluid (for example, air) flowing outside by evaporating refrigerant (liquid phase refrigerant) flowing inside to absorb heat from the fluid.
A refrigerant evaporator includes first and second evaporation units, each of which has a heat-exchanging core portion formed by stacking multiple tubes and a pair of tank portions connected to both ends of the multiple tubes. The first and second evaporation units are disposed in series in a flow direction of the fluid, and first tank portions of the respective evaporation units are coupled to each other via communication portions (see, for example, PTL 1 and PTL 2).
The refrigerant evaporator of PTL 1 and PTL 2 is configured in such a manner that when refrigerant that has flowed the heat-exchanging core portion of the first evaporation unit is made to flow into the heat-exchanging core portion of the second evaporation unit via the first tank portions of the respective evaporation units and a pair of the communication portions coupling the first tank portions, flows of the refrigerant are interchanged in a width direction (right-left direction) of the heat-exchanging core portions. In other words, the refrigerant evaporator is configured in such a manner that the refrigerant flowing the heat-exchanging core portion of the first evaporation unit on one side in the width direction is made to flow into the heat-exchanging core portion of the second evaporator portion on the other side in the width direction using one of the pair of communication portions, while the refrigerant flowing the heat-exchanging core portion of the first evaporation unit on the other side in the width direction is made to flow into the heat-exchanging core portion of the second evaporation unit on the one side in the width direction using the other communication portion.
The refrigerant evaporator described in PTL 1 enhances distribution of the refrigerant in the heat-exchanging core portion of the second evaporation unit by providing a partition plate inside an upper tank portion of a windward evaporation unit disposed on an upstream side in a flow direction of the fluid to divide a tank interior in a top-down direction and by providing the partition plate with through-holes.
Regarding the refrigerant evaporator described in PTL 2, let AA be a refrigerant channel through which a refrigerant flowing the heat-exchanging core portion of the first evaporation unit on one side in the width direction is passed to the heat-exchanging core portion of the second evaporation unit so as to flow on the other side in the width direction, and BB be a refrigerant channel through which a refrigerant flowing the heat-exchanging core portion of the first evaporation unit on the other side in the width direction is passed to the heat-exchanging core portion of the second evaporation unit so as to flow on one side in the width direction. Then, during a low flow rate operation during which a flow rate of refrigerant circulating in the refrigeration cycle is low, a case where an entire liquid phase refrigerant flows the refrigerant channel AA whereas the liquid phase refrigerant does not flow the refrigerant channel BB at all may possibly occur.
In such a case, because the liquid phase refrigerant flows the refrigerant channel AA, the liquid phase refrigerant flows the heat-exchanging core portion of the first evaporation unit on one side in the width direction and the heat-exchanging core portion of the second evaporation unit on the other side in the width direction. Hence, when the refrigerant evaporator is viewed in a flow direction of blown air, the liquid phase refrigerant flows an entire overlapping region in the heat-exchanging core portion of the first evaporation unit and the heat-exchanging core portion of the second evaporation unit.
In the refrigerant evaporator in which the liquid phase refrigerant is disturbed as above, blown air can be cooled sufficiently because the refrigerant absorbs sensible heat and latent heat from the blown air in the heat-exchanging core portion of either one of the evaporation units.
In order to distribute the liquid phase refrigerant as above during a low flow rate operation, it is necessary, in an inlet-side tank portion from which the refrigerant is distributed to the heat-exchanging core portion of the first evaporation unit, to pass the refrigerant from a refrigerant inlet portion from which refrigerant is introduced to a position opposing a boundary between two heat-exchanging core portions of the second evaporation unit (hereinafter, referred to as the boundary opposing region).
PTL 3 discloses a refrigerant evaporator that enhances distribution of a liquid phase refrigerant by providing a nozzle to a refrigerant inlet portion so as to direct the liquid phase refrigerant to an inner side (an end on the opposite side to the refrigerant inlet portion) of an inlet-side tank portion during a low flow rate operation.